PB2530: DIXON-BASED R2* MRI AS AN INTEGRATION/SUBSTITUTE OF STANDARD T2*/R2* IN THE EVALUATION OF IRON OVERLOAD IN THE UPPER ABDOMEN
Authors: Valeria Maria Pinto, Lorenzo Bacigalupo, Barbara Gianesin, Andrea Cazzato, Sabrina Quintino, Gian Luca Forni
Journal: HemaSphere (2023)

Topic: 27. Thalassemias Background: In magnetic resonance imaging (MRI) relaxometry a dedicated software is needed to obtain standard T2*/R2* values for iron overload evaluation in patients (pts) with Transfusion Dependent Thalassemia (TDT). Echo asymmetry and least square estimation-IQ (IDEAL-IQ) is a Dixon-based MRI sequence that allows measurement of R2* values without a dedicated software. Aims: To compare measurements of R2* in the upper abdomen (liver, pancreas, vertebra) between standard T2*/R2* multiecho sequences and the ones obtained from R2* IDEAL-IQ in TDT pts. Methods: Standard T2*/R2* and R2* IDEAL-IQ measurements were performed with a 1.5T scanner for each pt in the same session. Data were analyzed with linear regression, Pearson’s correlation coefficient (Rp) and Bland-Altman (BA) analysis. Results: 60 TDT pts (25 males, 42.5±9.5 years) were evaluated for R2* with standard T2*/R2* method and IDEAL-IQ in the period from 01/01/2019 to 31/12/2021. All pts had at least one evaluation of R2* in the liver, 55/60 in the pancreas and 59/60 in the vertebra. The 64% of pts had multiple evaluations within a time interval of (1.36±0.49) years. Figure reports comparisons between the two methods for liver, pancreas and vertebra. LIVER. Very good agreement between the two methods (Rp=0.990, 95%CI 0.984-0.994, p<0.001). The bias estimated with the BA-analysis was -0.35 Hz (95% CI: -4.14, 3.43 Hz), range of agreement -29, 28 Hz. Three pts with higher values of R2* were outside of the range of agreement, for them the standard method returned lower estimations of R2* than IDEAL-IQ. Differences of the methods versus their averages showed a negative coefficient regression (-0.11, 95%CI -0.15,-0.076, R2=0.39) indicating that IDEAL-IQ sequence returned higher values of R2* as the iron overload increased. Variations between two consecutive evaluations of R2* were available for 39 pts: comparison between the 2 techniques relatively to consecutive evaluations showed a positive coefficient of linear regression of 1.02 (95% CI: 0.95-1.09, R2=0.96) and Rp=0.98 (95% CI: 0.96-0.99). PANCREAS. Good agreement between the two methods (Rp = 0.81, 95% CI: 0.69-0.89, p<0.001). The estimated bias was 15.2 Hz (95%CI: 7.0-23.3 Hz), range of agreement -44, 74 Hz indicating that IDEAL-IQ returned lower evaluations of R2* respect the reference method. Differences of the methods versus their averages didn’t reach the statistically significant threshold (p=0.06). Variations between two consecutives measurements of R2* were available for 35 pts; comparison between the 2 techniques relatively to consecutive evaluations showed a positive coefficient of linear regression of 0.37 (95% CI: 0.22-0.52, R2=0.44) and Rp=0.67 (95% CI: 0.43-0.82). VERTEBRA. Very good agreement between the two methods (Rp = 0.95, 95% CI: 0.92-0.97, p<0.001). The estimated bias was 14.6 (95% CI: 6.0,23.2 Hz), range of agreement -50, 79 Hz. The comparisons of the differences of the methods versus their average values showed a positive coefficient of regression (0.23 95%CI: 0.15, 0.31, R2=0.36). Variations between two consecutive measurements of R2* were available for 38 pts; the coefficient of linear regression was 0.63 (95% CI: 0.50-0.76, R2=0.73) and Rp=0.85 (95% CI: 0.73-0.92). Summary/Conclusion: Our data suggest that R2* values from IDEAL-IQ can confirm and/or replace R2* values obtained from standard T2* sequences, with the advantage that IDEAL-IQ does not require a dedicated post processing software.Keywords: Thalassemia, MRI, Iron overload, beta thalassemia